1. Field of the Invention
This invention relates to fasteners, and particularly to surgical fasteners used to join body tissue.
2. Description of the Prior Art
Fasteners have been used surgically to eliminate the need for suturing, which is both time consuming and inconvenient. In many applications the surgeon can use a stapler apparatus, i.e., a fastener implanting device loaded with surgical fasteners to accomplish in a few seconds what would have taken many minutes to perform by suturing. This reduces blood loss and trauma to the patient.
Surgical fasteners have been in the form of ordinary metal staples, which are bent by the delivery apparatus to hook together body tissue. Also, two-part fasteners have been used, as illustrated in U.S. Pat. No. 4,506,670 in which a barbed fastener portion is used in conjunction with a retaining piece to hold the fastener in place.
Typically, the two part fastener comprises a back span and two barbed prongs which are engaged and locked into a separate retainer piece In use, the fastener is pressed into the body tissue so that the barbs penetrate the tissue and emerge from the other side where they are then locked into the retainer piece. The retainer prevents the fastener from working loose from the tissue. The two piece fasteners usually cannot be unlocked and are not removable. For this reason, they can be made of a bioabsorbable material.
Korthoff, et al., U.S. Pat. No. 4,667,674, herein incorporated by reference, discloses a two part surgical fastener comprising a fastener member and a retainer member. The fastener member has a base, and a pair of prongs extending perpendicularly from the base. The prongs are spaced inward from the respective ends of the base in order to prevent splaying of the prongs, and to improve hemostasis.
The two piece fasteners require the staple delivery apparatus to have access to both sides of the tissue. Usually, such devices have a U-shaped member into which tissue is inserted. The stapler apparatus has a fastener holder and an anvil which are pivotally connected at one end, and mounted on the legs of the U-shaped support structure. See, for example, Green U.S. Pat. No. 4,402,445, which discloses a surgical fastener and means for applying same. In a surgical operation, the tissue to be joined is positioned between the fastener holder and the anvil, which contains the fastener retainers. The fasteners are ejected from the holder into the tissue, and the prongs are locked into the retainers.
Certain types of wounds or incisions in fascia tissue require that the two edges of the wound or incision be held together in close approximation in order to promote proper healing. The fasteners described in the above-cited patents are designed for preventing bleeding by improving hemostatis, but they are not designed for holding two edges of a wound together. Green, U.S. Pat. No. 4,610,250 discloses a two part surgical fastener in which the retainer portion has a camming surface for bending two prongs of the fastener inward. When the fastener is properly positioned across a wound the bent prongs will maintain the edges of the wound in close adjacency until the fastener is biologically absorbed. This fastener, too, requires an applying instrument to have access to both sides of the body tissue.
In some applications, however, it is not possible to have access to body tissue from two opposite directions. For example, in skin grafting applications one can only apply fasteners from a stapler positioned above the skin.
The prior art includes many examples of surgical staplers which do not enclose the body tissue between an anvil and fastener holder. For example, surgical staplers such as those described in U.S. Pat. No. 3,643,851 and U.S. Pat. No. 4,618,086 approach the skin from one direction. However, they require the use of staples which are malleable enough to be crimped by an anvil so that the prongs hook into the tissue. Typically, such staples are made of metal and are not bioabsorbable. They must be removed by another device, such as a staple extractor. Furthermore, such staples are more useful for joining tissue layers laterally, as for example in closing wounds in skin or fascia, and, although useable, they are not optimum for laminarly fastening one layer of tissue onto another as in skin grafting.
Hence there is a need for a bioabsorbable surgical fastener which is capable of being delivered into the surface of body tissue from one direction, which can join layers of tissue both laterally and laminarly as required in skin grafting applications, which provides a biasing force to hold adjacent edges of body tissue in close approximation, and which does not have to be removed from the body (a painful procedure).